What were the traits associated with the river Lethe in 2nd edition Planescape material?

What were the traits associated with the river Lethe in 2nd edition Planescape material?

Everybody know what happens if you touch the river Styx: instant amnesia. But what about the river Lethe? Also, where was it located - I want to say on Baator, but I'm not sure. (I wish the full search engine were back up on this site, it would save me having to make posts like this!) Any info appreciated...

The River Lethe flows through Nessus, dropping into the trenches and trickling its way across the layer. That’s all anyone knows about the layer, for there’re few souls who’ve gotten in - and a berk can count on one hand the ones who’ve gotten out.

Nothing of its properties is mentioned, though the 1st edition Manual of the Planes says its properties are identical to the River Styx, except "Charon and his servants never appear on its shores." It also says that the Lethe "is said to link to certain Prime Material Planes in the same way as Yggdrasil and Mount Olympus." I riffed on that in this article on Canonfire!, working off the 3rd edition adventure "Road to Oblivion" by Penny Williams and "101 Wonderous Whereabouts," from Dragon #281, both of which featured the River Lethe flowing into the Material Plane.

In Planes of Conflict the Lethe is described as "the sweet waters of forgetfulness," but the source doesn't elucidate.

The River Lethe is noted as flowing through Nessus, Baator, and Hades' Realm, Pluton, Grey Waste. In fact, the river is something of a mystery. It rises somewhere in Chronias, Mt. Celestia, alongside the Euonë, it is told. It then flows down every layer of the Mountain, running in a broad, straight canal through Yetsirah, and thence wends its way down to the slopes of Lunia. However, it does not flow into the ocean there, but rather enters a cave and flows away into the depths of the Mountain, emerging in Nessus, of all places. Quite how Lunia is linked to Nessus is unclear, because the Nessus end of the river is always guarded by fiends. Some say that the enigmatic Lord of the Ninth seals it himself from time to time. Having thus entered Nessus, it flows parallel to the Styx into Pluton, where it eventually joins it in Hades' Realm. Lethe is called the River of Forgetfulness: Whoever drinks it forgets everything, just as with the Styx. However, unlike the Styx there is a way of retrieving lost memories from Lethe: simply walk upstream one mile for every year of life forgotten.

Not to self-promote too much, but this index might be a useful resource in the future for questions like this. It's got all 2e Planescape products, and a good portion of 3e. :D

(I need to get back to it some time and start working on more sources, though; it has some issues of Dragon, but I planned to bring in more and never had the chance.)

From this we can see that, going along with what Kaelyn had pointed out before, there's also a reference to the Lethe's memory-loss effects in Planewalker's Handbook in the "Blessed Forgetfulness" spell description. As for where it's found, in addition to the reference to Nessus that Kaelyn pointed out in her post, On Hallowed Ground established the Lethe as also flowing through the Underworld, Hades' domain.